Methods and apparatus for lubricating suspension components

ABSTRACT

Methods and apparatus for lubricating suspension seals by pumping fluid to the seals using a compression or rebound action of a suspension component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a Continuation of and claims the benefit ofco-pending U.S. patent application Ser. No. 15/442,532, filed on Feb.24, 2017, entitled “METHODS AND APPARATUS FOR LUBRICATING SUSPENSIONCOMPONENTS”, by Galasso et al., having Attorney Docket No.FOX-P9-03-08-US.C1.D1.C2, assigned to the assignee of the presentapplication, which is incorporated in its entirety herein by referencethereto.

The patent application having Ser. No. 15/442,532 is a Continuation ofand claims the benefit of U.S. patent application Ser. No. 14/292,263,filed on May 30, 2014, now U.S. Issued U.S. Pat. No. 9,599,182, entitled“METHODS AND APPARATUS FOR LUBRICATING SUSPENSION COMPONENTS”, byGalasso et al., having Attorney Docket No. FOX-P9-03-08-US.CON.DIV,assigned to the assignee of the present application, which isincorporated in its entirety herein by reference thereto.

The patent application having Ser. No. 14/292,263 is a divisional of andclaims the benefit of U.S. patent application Ser. No. 14/166,754, filedon Jan. 28, 2014, now abandoned, entitled “METHODS AND APPARATUS FORLUBRICATING SUSPENSION COMPONENTS”, by Galasso et al., having AttorneyDocket No. FOX-P9-03-08-US.CON, assigned to the assignee of the presentapplication, which is incorporated in its entirety herein by referencethereto.

The patent application having Ser. No. 14/166,754 is a continuation ofand claims the benefit of U.S. patent application Ser. No. 12/554,756,filed on Sep. 4, 2009, entitled “METHODS AND APPARATUS FOR LUBRICATINGSUSPENSION COMPONENTS”, by Galasso et al., now U.S. Issued U.S. Pat. No.8,672,096, having Attorney Docket No. FOX-P9-03-08-US, assigned to theassignee of the present application, which is incorporated herein in itsentirety by reference thereto.

The U.S. patent application Ser. No. 12/554,756 claims priority to andbenefit of U.S. provisional patent application 61/094,324, filed Sep. 4,2008, entitled “METHODS AND APPARATUS FOR LUBRICATING SUSPENSIONCOMPONENTS”, by Galasso et al., having Attorney Docket No.FOXF/P9-03-08, assigned to the assignee of the present application,which is incorporated herein in its entirety by reference thereto.

FIELD OF THE INVENTION

Embodiments of the invention generally relate to methods and apparatusfor use in suspension assemblies. Particular embodiments of theinvention relate to methods and apparatus useful for lubricatingcomponents of telescopic vehicle suspension.

BACKGROUND

Vehicles, including wheeled vehicles, are typically suspended to absorbshock encountered while traversing uneven terrain. Fundamental vehiclesuspensions for controlling vehicle body motion and handlingcharacteristics during vehicle travel over uneven surface are well-knownin the art. Wheeled vehicles usually include one vehicle suspensionassembly per wheel so that each wheel may absorb shock independently.Vehicle suspensions typically comprise many components, including ahydraulic cylinder with an internal piston connected to a central pistonrod, which reciprocates within the cylinder to produce damping forces.

Damping forces created by the vehicle suspension have a major influenceon the overall dynamic performance of a vehicle. A wide range of dynamicconditions are encountered during typical vehicle motion over varioussurface and terrain features. For example, these features and conditionsinclude large and small bumps, sharp-edged bumps and round-edged bumps,close-spaced bumps and wide spaced bumps, stutter bumps and gradualundulating bumps, and so forth. Thus, the vehicle suspension undergoes awide range of tough conditions that puts pressure on the functionalityof its internal components. What is needed are vehicle suspensionassemblies that better accommodate these performance requirements, asthere exists many limitations to the present state of vehicle suspensiontechnology.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the present technology forlubricating suspension components, together with the description, serveto explain principles discussed below:

FIG. 1 is a schematic of a front suspension assembly in the form of afork.

FIG. 2 is a cut away view of a bicycle fork embodiment as disclosedherein.

FIG. 3 is a cut away view of a coil-sprung embodiment of a suspensionfork that may be adapted for use with the embodiments disclosed herein.

FIG. 4 is a cut away view of a bicycle fork that may be adapted for usewith the embodiments disclosed herein.

FIG. 5 is a cut away view of a bicycle leg embodiment as disclosedherein.

FIG. 6A is a ball bearing bushing embodiment as disclosed herein.

FIG. 6B shows the dimensions for the ball bearing bushing embodiment ofFIG. 6A as disclosed herein.

FIG. 6C shows the specification for the ball bearing bushing embodimentof FIG. 6A as disclosed herein.

DESCRIPTION OF EMBODIMENTS

Vehicle wheel suspension often includes a damping mechanism fordissipating energy (e.g. from inertial wheel movement induced bydisparities in the terrain over which the vehicle travels) and a springmechanism for storing energy to rebound a compressed suspension to anuncompressed state. Damping assemblies often convert wheel movement intoheat by means of fluid friction in a dashpot type device. Springmechanisms may take many forms including, coiled springs, elastomerbumpers, compressible fluid (e.g. gas, silicone oil), suitablecombinations thereof or other suitable energy storage mechanisms.Vehicles having a single front wheel, such as for example motorcyclesand bicycles, often have front suspension assemblies in the form of a“fork” as shown in FIG. 1. The fork 34 shown in FIG. 1 includes lowerleg tubes 46 and 50 having upper leg tubes 44 and 48 telescopicallyengaged respectively therewith. Crown 52 holds the telescopic fork legsin spaced relation to steering tube 54. Drop outs 56 accommodate theaxle of a front bicycle wheel. The fork shown includes right leg 40 andleft leg 42. The fork 34 shown in FIG. 1 is similar to suspensiondisclosed in U.S. Pat. No. 7,163,222 which patent is incorporatedherein, in its entirety, by reference.

FIG. 3 and FIG. 4 show embodiments of suspension that may be adapted foruse with the systems and mechanisms described herein. FIGS. 3 and 4illustrate a coil-sprung embodiment of the suspension fork, indicatedgenerally by the reference character 34.

The coil-sprung fork embodiment 34 utilizes a pair of positive coilsprings to provide an expansion force on the fork 34. A first spring 320is located in the right fork leg 40, while a second spring 322 islocated in the left leg 42. An air spring arrangement may be used inlieu of or in conjunction with a coiled spring. With a coil spring 320,322 located in each of the fork legs 40, 42, respectively, the expansionforce on the fork 34 is substantially balanced between the fork legs 40,42. This enhances the coaxial telescopic motion of the upper legs 44, 48relative to the lower legs 46, 50 during compression and rebound forsmooth motion with reduced binding.

The first spring 320 is positioned in the right leg 40 between thedamper cap assembly 104 and the cartridge tube cap 108. A pair ofspacers, including a first spacer 324 and a second spacer 326, areinterposed between the damper cap assembly 104 and the first spring 320.In one embodiment the spacers 324, 326 are substantially C-shaped sothat they may be easily removed from the damper shaft 102 in a radialdirection. Optionally, the spacers 324, 326 are configured to engage thedamper shaft 102 in a snap fit arrangement.

A spring guide 328 is positioned between the first spring 320 and thespacer immediately adjacent the first spring 320 (spacer 326 in theillustrated embodiment) to assist in keeping the spring 320 concentricwith the damper shaft 102. The cartridge tube cap 108 functions as aspring guide for the lower end of the first spring 320. However, aseparate spring guide member may also be provided.

The second spring 322 is positioned in the left leg 42 between thespring cap assembly 80 and the upper spring stop 95. A first spacer 324and a second spacer 326 are positioned between the spring cap assembly80 and the spring 322. Desirably, the first and second spacers 324, 326are substantially identical to the spacers described above in relationto the first spring 320.

A preload adjuster assembly 330 is provided to allow adjustment of thepreload on the second spring 322. The preload adjuster assembly 330generally comprises an adjuster cap 332, an adjuster shaft 334, a barrel336 and an adjuster knob 338. The adjuster cap 332 is sealingly engagedwith upper open end of the upper tube 48. The cap 332 includes a centralaperture which allows the adjuster shaft 334 to pass through, preferablyin a sealed arrangement. The adjuster knob 338 is fixed to the adjustershaft 334 by fastener 340 such that rotation of the adjuster knob 338results in rotation of the adjuster shaft 334. A ball detent assembly341, substantially similar to those described above, may be providedbetween the adjuster cap 332 and the adjuster knob 338 to define aplurality of preload adjustment positions.

The barrel 336 is threadably engaged with the adjuster shaft 334 andengages the second spacer 326. In addition, the barrel 336 includes aball pocket for holding a ball bearing 342, which rides within an axialgroove 344 defined by the adjuster cap 332. This arrangement preventsthe barrel 336 from rotating relative to the adjuster cap 332.Accordingly, rotation of the adjuster shaft 334, via the adjuster knob338, results in translation of the barrel 336 relative to the adjustercap 332. A change in the axial position of the barrel 336 alters thepreload force on the spring 322.

The upper spring stop 95 is attached (e.g. roll-crimped) to a plungerrod 346 which extends upward from the closed end of the lower fork tube50. The upper spring stop 95 includes an o-ring 348 which serves as aspring guide for the lower end of the spring 322. The o-ring 348 ispreferred because it's compressibility allows a single size of o-ring toaccommodate a number of different spring inner diameters. The innerdiameter of a spring may vary with different spring rates, therefore,the o-ring 348 allows a number of springs 322 having varying springrates to be used with the suspension fork 34. A negative spring chamber94 is defined between the upper spring stop 95 and the lower spring stop92. In one embodiment a single negative spring 96 is provided, ratherthan the dual negative coil spring arrangement of previous embodiments.

The fork assembly 34 of FIGS. 3 and 4 is capable of being adjusted forvarying amounts of travel, or total distance between it's fullycompressed and fully extended positions. With reference to FIG. 4, thefork 34 has been configured to have less travel than the fork 34 asconfigured in FIG. 3. To accomplish this, the spacers 324, 326 of theleft leg 42 were moved from their position between the upper end of thespring 322 and the spring cap assembly 80 to a position below theplunger rod 346. Specifically, the upper spring guide 99 is sliddownward on the plunger rod 346 and the spacers 324, 326 are positionedbetween the upper spring guide 99 and the upper spring stop 95. Thislowers the upper tubes 44, 48 relative to the lower tubes 46, 50 andshortens the travel of the fork 34 by the combined length of the spacers324, 326. In order to accommodate the shorter travel configurationwithout altering the preload on the first compression spring 320, thespacers 324, 326 (FIG. 3) are removed from the right fork leg 40.

In one embodiment the first spacer 324 is approximately 20 mm in lengthand the second spacer 326 is approximately 25 mm in length. The travelof the suspension fork 34 as configured in FIG. 3 is approximately 125mm. As configured in FIG. 4, the travel is reduced to 80 mm. Optionally,only one of the spacers 324, 326 may be positioned below the upperspring stop 95 while the other spacer remains positioned above thespring 324. With this configuration, the fork travel would be shortenedby the length of the spacer positioned below the upper spring stop 95,either 20 mm or 25 mm. The corresponding spacer 324, 326 may be removedfrom the right fork leg 40, to maintain the desired preload on thespring 320, as described above. Additionally, varying spacerconfigurations may be used. For example, the spacers 324, 326 may bereplaced by a single spacer. Also, spacers of other lengths may be used.

U.S. Pat. No. 7,374,028 which patent is incorporated herein, in itsentirety, by reference shows a shock absorber that may be adapted foruse with the methods, systems and mechanisms described herein. Forexample referring to FIG. 12 of that patent, a portion of the fluid,displaced by shaft 120 during compression may be ported and conductedthrough the lower seal cap (by means of a flow path) surrounding shaft120 and including shaft seals, to lubricate the shaft seals and thenreturn to the primary reservoir.

FIG. 2 and FIG. 5 show a cut away view of an embodiment of a bicyclefork (suspension fork 34) and leg respectively. The numbers shown anddiscussed herein in reference to FIG. 5 are, for the purposes of thedescription herein, applicable only to FIG. 5 herein so as not to beconfused with their appearance elsewhere (although the same numbers mayindicate similar corresponding elements elsewhere), for example in U.S.Pat. No. 7,163,222. Those same numbers may appear in U.S. Pat. No.7,163,222 but such appearance is not subject to specific treatmentherein (although those discussions and parts are incorporated byreference in their context along with U.S. Pat. No. 7,163,222). Inrelevant detail, as shown in FIG. 2, are lower leg tubes 46 and 50having upper leg tubes 44 and 48 telescopically engaged respectivelytherewith. In the asymmetric fork embodiment of FIG. 2, leg 46/44comprises a damping assembly while leg 48/50 comprises spring assembly.Optionally one leg may, or both legs may, comprise both a damping andspring assembly. In one embodiment, each fork leg includes a sealassembly 68/70, bushings 64 and 66 and a reservoir 114 containing alubricating fluid (e.g. hydraulic damping oil). In one embodiment, thereservoir 114 tends to hold fluid toward a lower end 200 thereof due tothe effects of gravity.

FIG. 2 shows other components of a suspension fork 34 that are notdescribed in detail, but are depicted nonetheless for contextualpurposes. These components are damper cap assembly 104, right leg 40damper assembly 76, rebound damping assembly 106, compression chamber112, upper compression passage 120, rebound rod 118, inner surface ofthe damper shaft 102, rebound chamber 110, steerer tube 54, crown 52,cap 91, valve 90, spring cap assembly 80, seal 81, positive air springchamber 88, left leg 42, suspension spring assembly 74, spring piston86, pin 89, radial through-hole 85, through-hole 87, pin 97, springguides 99, snap ring 93, upper spring stop 95, outer negative spring 96,negative spring chamber 94, inner spring 98, spring plate 92, centralaperture 101, spring piston rod 84 and bottom-out bumpers 72.

In one embodiment, each fork leg comprises a seal and wiper assembly,located at the entrance or upper opening of each lower leg tube 46 and50, to seal fluid (e.g. oil) into the telescopic leg and/or to keepdebris out of the telescopic leg. The seal assembly seals against anouter surface of the upper leg tube 44/48 as it moves telescopicallyrelative to the opening. In the shown embodiment, the seal assemblycomprises wiper seal 68 and foam ring 70.

Referring to FIG. 5 for detail of one embodiment, it is desirable thatthe wiper seal or main seal 68 be lubricated during use. Foam ring 70retains hydraulic oil (e.g. damping fluid) in the region of ring 70 anddistributes that onto upper leg tube 44, as upper leg tube 44 movesaxially past the foam ring 70 and the wiper seal 68, so that wiper seal68 can be lubricated. In one embodiment damping oil is supplied to theannular region of foam ring 70 and wiper seal 68 from reservoir 114 viafluid conduit 201.

The principles disclosed herein are equally applicable, by way ofexample, to either leg (or both legs) of a vehicle fork such as thatshown in FIGS. 1, 2, 3, 4 and 5. For simplicity, an embodiment will bedescribed by reference to the one fork leg of FIG. 5 (as shown, forexample, from FIG. 2) which typifies in relevant respect the germanefeatures of the embodiment. As the fork leg exemplified in FIG. 5 isused on, for example, a bicycle over terrain, the upper leg tube 44telescopes in and out of the lower leg tube 46 in response to bumps ordepressions that are encountered by a wheel attached to the drop out 56(drop out 56 shown in FIG. 1) of the lower leg tube 46. During acompression stroke of the fork, caused by the wheel encountering a bump,the incursion of the upper leg tube 44, and particularly the lowerportion 202 of the upper leg tube 44 into reservoir 114 tends todynamically increase the pressure of the fluid in reservoir 114.Optionally such effect may be increased by adding an annular shapedsubstantially fluid tight end cap 203 inside or at the lower end ofupper leg tube 44. Optionally end cap 203 may be a fluid flowrestricting perforate fluid baffle. Optionally such end cap 203 mayinclude check valves allowing fluid to flow downwardly out of aninterior of upper leg tube 44 and into reservoir 114 but restrictingflow upwardly into the interior of upper leg tube 44 (from reservoir114). Miniature check valves (and other fluid flow elements) maycomprise, for example, such valves as shown, or of a type shown, in the“Technical Hydraulic Handbook” copyright 1996 by The Lee Company. 2Pettipaug Road, Westbrook, Conn. 06498 USA which handbook isincorporated herein, in its entirety, by reference. Additionally and asshown in FIG. 5, the damping piston rod 102 moves into compressionchamber 112 during a compression stroke and forces fluid fromcompression chamber 112, through a valve or valves in the lower end ofchamber 112, and into reservoir 114 thereby further increasing the fluidpressure in reservoir 114 and particularly a dynamic fluid pressuretherein.

In one embodiment the increased fluid pressure in reservoir 114 causeshydraulic fluid (e.g. oil) in reservoir 114 to enter fluid conduit 201at a lower end 204. It is noted that, because of the various annularflow restrictions (e.g. bushings 64, 66) between the lower end of thefork leg and the upper end, movement of upper leg tube 44 in and/or outof lower leg tube 46 does not create any appreciable dynamic fluidpressure change in the area of the seal assembly 68/70 including that inopen annular area 71 between the wiper seal 68 and the foam ring 70 andthe region of the foam ring 70. The increase in fluid pressure inreservoir 114 during a compression stroke therefore creates adifferential pressure between the reservoir 114 and the annular area 71and tends to push fluid from the reservoir 114 toward the open annulararea 71 via fluid conduit 201 (because flow though conduit 201 isrelatively unrestricted). With each compression stroke of the fork leg,some fluid is pushed into fluid conduit 201 at lower end 204 and movedupwardly past check valve 206. In one embodiment, as shown in FIG. 5,check valve 206 comprises a ball which is biased against a valve seatthere below by a spring. In operation, the ball may be dislodged fromthe valve seat (against which the ball is spring biased—not numbered) byfluid pressure in flow path 205 of fluid conduit 201, thereby allowingfluid flow in direction of flow 207. In order to unseat the ball againstthe force of the spring, the fluid pressure in flow path 205 must begreat enough that, when applied over the area circumscribed by the valveseat, it results in a force that is greater than the force exerted bythe spring. Fluid in the upper section 208 of flow path of fluid conduit201 is substantially blocked from flowing in a direction opposite thedirection of flow 207 because such flow counter to direction 207 wouldserve to increase the force exerted by the ball on the valve seat andwould therefore increase the closure force of check valve 206.

During a rebound stroke of the fork leg (in which upper leg tube 44 isaxially moving relatively upward and out of lower leg tube 46 and lowerportion 202 of upper leg tube 44 is correspondingly relieving pressureon reservoir 114) the check valve 206, having a “free flow” directionindicated by arrow 207 (and a flow check direction opposite of “freeflow”), holds the fluid pushed into the upper section 208 of the fluidconduit 201 against backflow toward reservoir 114. The rebound strokealso creates a dynamic pressure in reservoir 114 that is somewhat lowerthan the pressure in area 71. That differential pressure causes dampingfluid to be forced from the upper area 71, down though annulus 210 (pastbushings 64, 66) and back to reservoir 114 (because back flow throughconduit 201 is checked at valve 206.

As fluid (e.g. oil) fills upper (above the check valve 206) section 208,it ultimately flows into open annular space 71 through port 209 (pointof entry of fluid). The fluid in the open annular space 71 encountersthe wiper seal 68, an exterior of the upper leg tube 44, and the regionof foam ring 70 and foam ring 70. The fluid thereby lubricates the wiperseal 68 and the exterior of upper leg tube 44 and replenishes the fluidsaturation of foam ring 70. As foam ring 70 retains damping fluid withinits region it becomes saturated and excess fluid flows down past bushing64, through annular space 210, past bushing 66 and into reservoir 114.The fluid retained within the region of foam ring 70 remains availableto lubricate the exterior of upper tube 44 as the fork cycles. Thelubricating action is therefore relatively constant and not dependent onfluid surges that become available during fork compression strokes. Insuch a way, hydraulic fluid is circulated through the fork, to aretaining region and past the upper seal assembly by the pumping actionof the fork during fork compression strokes.

Optionally, one or more of the bushings 64 and 66 (of which there may bemore or less than two) may comprise cup or lip seals that allow fluidflow downwardly toward reservoir 114 but inhibit flow upwardly fromreservoir 114 and through annular space 210. Cup seals, lip seals orchevron seals comprise a cross section that includes one or morerelatively thin lips. Such a lip(s) typically seals fluid pressure byusing that pressure to increase the force per unit area between the lipand a diametric surface adjacent thereto. The principle of such“chevron” or “lip” type seals is described in U.S. Pat. Nos. 4,787,642and 5,246,236, each of which is incorporated, in its entirety, herein byreference. Note that in U.S. Pat. No. 5,246,236, seal 36 of FIG. 3 isdescribed as metal. Such seal 36 may also comprise in whole or part anelastomer or other suitable highly elastic material. In one embodimentan annular flow barrier (e.g. washer shaped) having check valves therethrough may be fixed in annulus 210 where such check valves areconfigured to check flow from reservoir 114 to annulus 71 and to allowflow from annulus 71 to reservoir 114. Optionally, the fluid conduit 201may be constructed by means of an annular space or partial annular spaceor channel(s) built around or within the wall of the lower leg tube 46.In one embodiment, the conduit or conduits (in parallel), andcorresponding flow path 205, 208, may be cast into the wall of the lowerleg tube 46. In such an embodiment a check valve containing ring barriermay be placed in the bottom of the reservoir 114 in sealing relation toan interior of the reservoir and configured such that fluid must passthrough the ring (or plug) in order to enter the equivalent lower end204 of the integral conduit(s). The one or more check valves in the ringare configured to allow fluid flow into the one or more equivalent flowpaths 205,208 toward annulus 71 and to check fluid back flow towardreservoir 114 (i.e. they are analogous to valve 206 but may be placed atthe entrance to the equivalent flow path 205, 208 rather than along thepath). In another embodiment, an additional cylindrical portion (notshown) is included that surrounds all or a portion of the lower leg tube46 and the flow path 205/upper section 208 of flow path comprises anannular fluid flow space space between an interior of the cylindricalportion and an exterior of the lower leg tube 46. Optionally the checkvalve(s) may comprise an elastic sleeve covering an exterior of lowerend port 204 (or other relevant port) such that fluid entering the flowpath 205, 208 must stretch (“burp” valve) the sleeve to exit thereservoir 114 and is prevented from flowing back by the sleeve as it isrecovered across lower end 204 following the exit of the fluid throughthat port. Such sleeve seals are shown as “expandable bands” 40 and 42in U.S. Pat. No. 6,415,895 which is incorporated herein, in itsentirety, by reference. Optionally the check valve may be at anylocation in the conduit, including immediately at the lower end 204.Optionally the fluid conduit 201 may include a plurality of check valvesat different locations along the fluid flow path. Optionally, the fluidconduit 201 may outlet back into the lower leg tube 46 at points otherthan port 209 (e.g. into a location or locations other than the openannular area 71). For example, the fluid conduit 201 may outlet directlyinto a side of the foam ring 70 and/or below the foam ring 70.Optionally, the fluid conduit 201 outlets at multiple points along thelength of the lower leg tube 46. For example, the fluid conduit 201 maymanifold into an interior of the lower leg tube 46 such that it outletsinto open annular area 71, the side of the foam ring 70, below the foamring 70, and into an outer surface of one or more bushings (e.g. 64,66). In one embodiment one or more of such bushings may include a radialhole or holes (e.g. distributed circumferentially) through a wallthereof and an inner diameter of lower leg 46 may be enlarged in aregion proximate such holes thereby creating a flow annulus around thebushing to distribute flow through the bushing holes. In one embodiment,the fluid flow path 208 is ported into the flow annulus region so thatpressurized fluid may be delivered, via the bushing holes, to an innerdiameter of the bushings during fork compression. Such an embodimentcreates a bearing layer of damping fluid which lubricates the surfacebetween the inner diameter of the bushing and the outer diameter of tube44. The fluid conduit 201 may outlet at any point or points of desiredlubrication or fluid introduction.

Optionally, bushings (e.g. bushings 64 and 66) may comprise linearmotion bearings as shown in FIGS. 6A, 6B and 6C. In use, a suspensionfork is typically positioned in a bicycle or motorcycle at a rake angle.More specifically, the steering tube (and hence the fork) is attached tothe vehicle at an angle from the vertical (e.g. rake), as opposed toabsolute vertical, to enable improved vehicle handling. An artifact ofthat angle is that the weight of the vehicle (and associated impulseload due to impact) bearing on the front wheel imparts not onlycompressive but also bending loads into the front fork and its legs.Such bending loads increase the relative sliding resistance between, forexample, the upper leg tube 44 and the lower leg tube 46 (by increasingthe normal/radial load on, for example a side of the bushing 64/66). Anadvantage of linear motion bearings is decreased apparent frictionbetween upper leg tube 44 and lower leg tube 66 due to decreasedfriction between the upper leg tube 44 and the interior of the bushing.Such decreased friction allows the suspension to move more freely, andbetter absorb shock despite the tube side loading incident to the rakeangle. Principles of linear bearings are described in U.S. Pat. Nos.5,622,434; 6,619,844; and 4,952,075; each of which is incorporated, inits entirety, herein by reference. Optionally an inverted (“inside out”)linear motion ball bearing bushing may be used and fixed to an exterioror the upper leg tube 44. In one embodiment a surface hardness treatmentis applied to an exterior of the fork leg engaging such a ball typebearing to reduce the effect of high localized bearing stress oncontacted portions of the fork leg. Surface treatments such a shotpeening, nitriding, carburizing or ceramic coating or any suitablecombination thereof or any other suitable surface treatment may be used.

In one embodiment, a ball bearing bushing as exemplified in FIGS. 6A, 6Band 6C includes circumferential fluid flow gaps and holes that arepositioned circumferentially (e.g. within the gaps) around at least aportion of the ball bearing bushing. These fluid gaps receive fluidflowing from fluid conduit 201. The holes in turn receive the fluidthrough the fluid gaps from the outer portion of the ball bearingbushing and deliver the received fluid to the inner portion of the ballbearing bushing. In one embodiment, the fluid gaps receive this fluidfrom a fluid holding region that holds the fluid prior to distribution.Such a region may deliver fluid based on depletion, and correspondinglower pressure, within the gaps (e.g. siphon effect). In one embodiment,the fluid holding region circumferentially surrounds at least a portionof the ball bearing bushing, wherein that portion includes at last oneof the fluid gaps. By the fluid gap sitting in, or adjacent, the fluidholding region, the fluid in the fluid holding region slowly leaks intothe ball bearing bushing through the fluid gap. In another embodiment, afluid channel runs from the fluid conduit 201 to the fluid holdingregion. The fluid channel delivers fluid from the fluid conduit 201 tothe fluid holding region, during operation of the vehicle suspension.

In one embodiment, the mechanisms and methods described herein areadapted and configured to function during a rebound stroke of asuspension system. In such case for example, the optional cup seals (orlip seals) proximate bushings 64 and/or 66 may be directionally reversedsuch that they prevent flow from the open annular area 71 in a directiontoward reservoir 114. In one embodiment, they (one or more) are fixedrelative to upper leg tube 44 so that they move relative to the lowerleg tube 46 during compression and extension. The seals may be fixedrelative to the upper leg tube 44 in a region such that they do notinterfere with the bushings (e.g. 64, 66) during compression orextension (i.e. rebound). A suitable location for such seal may be, forexample, proximate lower portion 202 of upper leg tube 44. Mounted assuch, the seals allow fluid to bypass, from below the seal to above theseal, during a compression stroke (upper leg tube 44 moving further intolower leg tube 46). During rebound, the seals retain the bypassed fluidand upward movement of the upper leg tube 44 relative to the lower legtube 46, pulls the retained fluid upward in lower leg tube 46 and towardopen annular area 71. In order to facilitate such upward movement past,for example, the bushings; the bushings (e.g. 64, 66) may be slottedaxially, from end to end, in one or more locations along an inner (orouter) surface thereof. In one embodiment, such axial slots are fittedwith miniature check valves such that fluid flowing from reservoir 114to open annular area 71 may “free flow” in that direction while beingchecked or blocked in the reverse direction. Optionally oralternatively, the slotted or axially drilled (end to end along in awall thereof) may be covered at an end closest to open annular area 71(e.g. an upper end) by an annular elastic “burp” seal that allows flowtoward open annular area 71 but recovers over the end of the bushing andprecludes flow in the opposite direction. Such “burp” seals operate in afashion similar (same in principle) to that described in relation to theelastic diameter covering bands discussed in reference to lower end 204herein. In one embodiment, the free flow direction 207 is the reverse ofthat indicated in FIG. 5 and fluid flow is checked in the directionindicated by free flow direction 207. Fluid that is “pulled up” by thereversed seals fixed to the upper leg tube 44, as in the foregoingdescription flows from open annular area 71 (after depositing in foamring 70 and wiper ring 68) into upper section 208 of flow path. From theupper section 208 of flow path, the fluid flows down through thedirection of free flow 207 check valve, into flow path 205, throughlower end 204 and back into reservoir (or chamber) 114. As described thecup seals will “swab” hydraulic fluid upwardly from reservoir 114 towardthe upper seal assembly on every rebound stroke. Principles of fluidpumping by “swabbing” (including lip or cup type seals) are described inU.S. Pat. Nos. 4,070,134 and 4,528,896, each of which is incorporated,in its entirety, herein by reference. With the free flow 207 of checkvalve 206 reversed, fluid conduit 201 serves as the return flow path forexcess fluid returning from the upper seal assembly to the reservoir 114(or chamber).

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be implementedwithout departing from the scope of the invention, and the scope thereofis determined by the claims that follow.

What is claimed is:
 1. A self-lubricating suspension comprising: an upper leg tube; a lower leg tube, said lower leg tube having an opening therein for telescopically receiving said upper leg tube, said upper leg tube and said lower leg tube telescopically moveable with respect to each other during operation of said self-lubricating suspension; a seal assembly coupled to said lower leg tube proximate said opening, said seal assembly configured to seal against an outer surface of said upper leg tube as said upper leg tube moves telescopically with respect to said lower leg tube; a fluid reservoir disposed at least partially between an inner surface of said lower leg tube and an outer surface of said upper leg tube, said fluid reservoir having a pressure therein, wherein said pressure is dynamically affected as said upper leg tube moves telescopically with respect to said lower leg tube; a fluid conduit, said fluid conduit in fluid communication with said fluid reservoir and said seal assembly, said fluid conduit defining a flow path extending between said seal assembly and said fluid reservoir, wherein said pressure, which is dynamically affected as said upper leg tube moves telescopically with respect to said lower leg tube, causes fluid to flow from said fluid reservoir into said fluid conduit, to said seal assembly, and then back into said fluid reservoir such that as said upper leg tube moves telescopically with respect to said lower leg tube said fluid flows through said fluid conduit and to said seal assembly to repeatedly provide said fluid to said seal assembly for generating lubrication between said upper leg tube and said lower leg tube and such that said self-lubricating suspension generates said lubrication as said upper leg tube moves telescopically with respect to said lower leg tube; and an annular space extending from said seal assembly to said fluid reservoir. 